Although not limited thereto, the invention is particularly useful in connection with underground cable pressure monitoring systems such as employed by Bell Telephone Laboratories Inc.
In one such known system, pressurized telephone cables are monitored by series of transducers which are mounted in groups and are connected together at a separate junction box which in turn is coupled by means of a spliced case to a cable which leads back to a monitoring or supervising system. An example of a manhole installation is illustrated in Bell Telephone Laboratories development letter LP 1696 which illustrates two pressure transducer housings AT-8652 and one terminal box AT-8653. This arrangement allegedly allows freedom in choice of mounting location for the transducer housings with the limitation that the terminal box must be mounted in horizontal or near horizontal position and in a certain specified attitude.
The junction box includes a housing which encloses a connector block which provides for joining wire pairs from a plurality of transducer housings to a stub which is provided as part of the junction box assembly. This stub can be spliced into a designated cable upon installation for transmitting electrical signals to a remote station.
The pressure transducers which are generally employed in the above are identified as AT-8651 which is a gas-pressure activated switching device by which the pressure of an air input can be determined by the value of electrical resistance measured between two output terminals in a general working air-pressure range of from 0 to 9.5 psig. This unit is not self-contained but must be attached for use to an air-tight cavity such as provided by a transducer housing referred to above as AT-8652. The connection of a cavity to a pressurized cable is effected by means of plastic air tubing.
The aforesaid housing assembly provides a mounting for 1 to 5 transducers in air-tight cavities which provide for air tubing connection to the pressurized telephone cables that are to be monitored.
The aforesaid arrangement is not only difficult to install and dismount but, moreover, requires substantial space for physical emplacement and is as well relatively expensive. It, moreover, does not provide for ease of electrical and pneumatic connection and does not provide optimal avoidance of air leakage or protection for electrical connections.